Waterjet Technology – Making gift items by water jet cutting

There is a time which can come in late Winter and very early Spring when demand declines and there is some free time for the occasional home project. Although many of us now know and understand how well waterjets and abrasive waterjet streams can cut material, this is still not that widely recognized by the General Public. This slack time can help to remedy that problem.

Uninformed ignorance of jet capabilities was certainly true for many years on our campus and seems to become more so again as the years pass since I retired. Further, at Conferences, I often heard the complaint that the industry needs to get its message out more clearly to a wider audience. The vast majority of potential industrial users are unaware of how well waterjetting in one of its forms could help solve their problems.

Now there are lots of ways of solving that problem, but today I want to talk about just one, the one we used to help us with the problem. It had to be something that would be used by those we gave it to. It had to be small, relatively cheap and quick to make and yet demonstrate some of the capabilities we wanted to show off. The answer ended up as a business card holder.

Figure 1. Business Card Holder – Missouri Miner female figure

University labs are generally cash strapped, and so the material had to be relatively cheap, so we used sheets of a light foam. This allowed us to cut out the figure parts using water alone (at around 20,000 psi) which significantly reduced the cost. Early in the design of the female figure (this was the third in a series where we cut a different shape each year) it was pointed out that relative body size was more critical with female figures, and so two different thicknesses of foam were used. The first was half-an-inch thick and used for the body and pins, while a quarter-inch sheet was used for the legs and arms.

Putting a small hole in the position of the eye allowed the model to show how precise and small a cut could be made through thicker material. The five pieces that made up the total were held together with two rectangular pins that were cut from the thicker stock and fitted through slots cut to their shape in the different parts.

One of the advantages of cutting these (and we cut parts for around 300 figures, and used virtually all of them each year) is that it was also possible, with relatively little trouble, to cut the campus identifier on a leg of the figure. With not a lot of space this was originally UMR and then changed to “S & T” when the campus changed its name.

Figure 3. A later model of the card holder with the campus ID cut into the leg by waterjet cutting

For speed in cutting, we only cut the letters in half the legs, though you may note that in this later version we also cut the connecting pins as round rod, rather than rectangular. In this way the figure could be repositioned as the owner decided what they wanted to do with them.

Basically, however they served as card holders, and having passed them around, (and provided them to senior campus officials as place card holders for dinner meetings) it has been amusing to see how avidly they were sought and kept by some of those to whom they were given.

Now we did not get to these figures in one step. The initial idea was to carve something out of rock, since the overall department was known as The Rock Mechanics and Explosives Research Center. However, if you are making something out of rock, particularly a person’s shape, they need to be larger, because of the weak strength of the rock.

The cost was also high, since the cuts had to be made with abrasive, and the rock had to be polished before it was cut. (Trying to polish the pick points after cutting led to several breakages, and this is something that is either perfect or worthless).

There are several good ideas that individual companies have which help sell their name and capabilities where the gifts are of metal and can be used for opening bottles or of some other benefit. But we could not afford the cost to cut a lot of pieces using abrasive, and nothing that we tried in metal had the cachet of the small miners.

In this case, the mascot of the campus is the Missouri Miner, and while the first model that we cut followed along the shape of that cartoonish figure, many of our graduates were going into coal mining, which is also my background, and so the second and third versions had coal mining helmets, and as a further demonstration of capabilities, a small circular cut in the helmet allowed a yellow rod to be put into the helmet to illustrate the miner’s cap lamp.

Where we were asked to prepare small souvenirs for another event we did use the Missouri Granite, but had learned this time to buy tiles that were already polished. Then all we had to do was to cut the shape of the state into the tiles, and then put a University logo sticker on the piece and we had our memento for the guests.

Figure 5. Small memento of the state shape carved out of granite tile by cutting with waterjet technology

This was for a specific occasion where the sponsor was willing to pay for both the cutting costs and the materials, but in order to keep costs down (since these were given away) the pieces had to be small. This particular run was one of the more difficult to keep inventory on, since several disappeared during the short time of the cutting runs (which we have found is an occupational hazard with “artistic” pieces where there are lots of temporary folk involved in our work).

Which is, I suspect, an entry for the last piece of advice on making such gifts, and that is to plan on making more than you think you need and, if possible, be able to make more if needed. In a later post I will write about where you can get some artistic help for relatively little cost to help with ideas such as this.